Method of manufacturing fully furnace hardened mated steel embossing rolls

ABSTRACT

A method of manufacturing a pair of mated steel embossing rolls which are fully furnace hardened. A pair of steel rolls are machined, except for the final grinding operation, and then fully furnace hardened. One roll has its surface normalized and is machine engraved. The engraved surface is flame hardened and mated to the other roll to produce a pair of fully hardened mated embossing rolls.

11mm Etates Patent [191 Broderick METHOD OF MANUFACTURHNG FULLY FURNACE HARDENED MATE!) STEEL EMBOSSING ROLLS [4 1 Apr. 16, 1974 3,214,310 10/1965 DiLeo et al 29/148.4 D

Primary Examiner-Thomas H. Eager [5 7] ABSTRACT A method of manufacturing a pair of mated steel embossing rolls which are fully furnace hardened. A pair of steel rolls are machined,v except for the final grinding operation, and then fully furnace hardened. One roll has its surface normalized and is machine engraved. The engraved surface is flame hardened and mated to the other roll to produce a pair of fully hardened mated embossing rolls.

6 Claims, 1 Drawing Figure pea a ABa JJ pea 5) METHOD OF MANUFACTURING FULLY FURNACE HARDENED MATED STEEL EMBOSSING ROLLS This invention relates to a method of manufacturing mated steel embossing rolls and more particularly to embossing rolls fully hardened.

Mated steel embossing rolls are made by a number of different techniques. One method for making such rolls is to machine engrave a pattern on the surface of an annealed or normalized roll, flame harden the roll, and mate the roll with pattern thereon to the surface of the second roll. When machine engraving the first roll, the roll must be in an annealed or normalized condition and once the pattern is engraved thereon, the surface of the roll is hardened. The pattern is mated to the second roll by acid etching techniques or otherwise engraved onto the second roll. If one or both of the mated embossing rolls is only hardened on its surface as in the case in prior machine engraving techniques, the roll will not, in many instances, withstand shocks and other forces produced when metallic strips or sheets are passed therebetween to be embossed, especially sheets which have folds, foreign objects, or uneven or irregular thickness. If the surface hardened rolls are hardened to greater depths, the patterns inthe roll may be distorted due to the extreme heats required to harden the rolls.

Fully hardened mated embossing rolls may be produced by standard photo engraving and acid etching techniques, however, the acid etching techniques undercut the pattern; that is, the acid eats away the sides of the pattern as well as the bottom of the pattern to produce patterns having very sharp edges which will tend to cut or mutilate the metal being embossed and will cause sticking to the rolls. With machine engraved rolls the processes which form the pattern in the female roll mayhave rounded edges and be contoured, however, in standard acid etching techniques this is not the case, and the recesses will have sharp edges with no contouring. Acid etching techniques do allow for the production of fully hardened rolls whereas machine engraving techniques, for the most part, only allow for the production of surface hardened rolls.

One method of producing mated metal embossing rolls which are hardened to their full depth is described in US. Pat. No. 3,048,512 wherein an additional master roll is made which is hardened after being engraved and is used to produce the mated metal embossing rolls from fully hardened rolls. This technique, of course, is costly both in materials and labor as an additional full sized roll must be produced in order to produce the final fully hardened matched embossing rolls, however, this technique of necessity has found acceptance in the industry.

I have now discovered a method for manufacturing a pair of mated steel embossing rolls which are fully furnace hardened and which overcome the disadvantages of the prior techniques.

In my new method the first roll is machine engraved. As mentioned above, the machine engraving allows for the recesses in the pattern to have rounded edges and be contoured which are much more desirable in the embossing of certain types of materials. Furthermore, my new method does not require that any additional roll be made in the manufacture of my embossing rolls and hence has economical benefits in time, labor and expense.

In accordance with the present invention-a pair of steel rolls, either alloy or high carbon steel, are machined except for the final grinding operation, with allowances made for shrinkage of the outside diameter of one of the rolls. The machined rolls are furnace hardened so that they are fully hardened including all journals, trunions, etc. One of the rolls of the machined pair of rolls is sized so as to allow for a shrinkage in diameter of about 0.040 to 0.050 inches during my new process. The type of pattern to be engraved in the pair of rolls will determine the relationship of the diameters of the pair of rolls before they are fumaced hardened so that the final set of mated steel rolls will have the correct diameter needed. One of the rolls has its outer surface normalized preferably by a flame hardening operation. The normalizing step softens the outer surface and causes the roll to shrink slightly in diameter. The normalized roll has its outer surface turned and ground so that it is exactly the correct diameter needed. The normalizing step softens the surface of the roll to a depth of from between 54; inch to A inch. This softened surface is machine engraved by standard machine engraving techniques and the recesses contoured and rounded as desired. After the surface is engraved with the desired pattern the roll is flame hardened to harden the surface of the roll to substantially the same degree as the inner portion of the roll. The engraved roll is mated to the other previously furnace hardened roll by conventional procedures.

The present invention will be more fully described in conjunction with the accompanying drawings wherein: the FIGURE is a flow sheet showing the various steps in the process of the present invention.

A pair of alloy steel rolls, such as alloy 4150 steel or high carbon steels in the 1,050 to 1,055 range, are ground except for final machining and furnace hardened by standard furnace hardening techniques (Box 1). The outside diameter of one of the rolls is slightly oversized; that is it has a slightly greater diameter than will be required for the final mated roll. This difference in diameter should be approximately 0.040 to 0.050

1 inches. Both of the rolls at this point have a Rockwell C hardness in the range of 45 to 55 or 60.

The slightly oversized roll is passed through a flame hardening technique to normalize the entire face or surface of the roll (Box 2). This normalizing pass re duces the Rockwell C hardness of the surface of the roll so that it will readily accept standard mill and dye machine engraving. The normalizing pass slightly reduces or shrinks the roll and the roll is reground to provide exactly the correct diameter for the final mated roll.

The normalizing process softens the roll to a depth of from about one-eight to-one-fourth of an inch. The roll with the normalized surface is machine engraved by standard mill and dye techniques (Box 3). Any desired pattern may be engraved in the roll.

After the roll has been machine engraved, the surface of the roll is flame hardened so that it will have a Rockwell C hardness in the 45 to the 60 range (Box 4).

The flame hardened engraved roll is mated to the other previously furnace hardened roll by standard acid resist and etching techniques or by other similar conventional procedures (Box 5).

The resultant rolls are a perfectly matched set of steel embossing rolls fully hardened.

The rolls may be used for the register embossing or standard embossing of various types of materials such as metal sheets or strips, foils, laminates, paper, and the like.

The following example is a specific method for pro ducing a set of matched steel embossing rolls in accordance with the present invention.

A pair of high carbon 1,050 steel rolls are furnace hardened. Each of the rolls is 50 inches long and one of the rolls has a diameter of 14.020 inches and the other roll has a diameter of 14.065 inches. The set of rolls is placed in a furnace and heated to a temperature of 1,675 F. for to 12 hours. The rolls are quenched to produce a Rockwell C hardness throughouteach roll of 50 60. The roll having the 14.065 diameter is passed through a flame hardening machine to normalize the surface of the roll. The temperature of the surface of the roll is raised to 1,800 F. to normalize it to a depth of from about one-eighth to one-fourth of an inch. The roll having the normalized surface is turned and machine ground to a diameter of 14.000 inches.

' The normalized roll is machine engraved with a standard hand engraved hardened mill in a pattern of Walker. The-machine engraved roll is passed through a flame hardening furnace and the surface of the roll is flame hardened at a temperature of l,675 F. for about 50 minutes to produce a Rockwell C hardness on the surface of 50-60, equivalent to the Rockwell C hardness on the surface of 50-60, equivalent to the Rockwell C hardness in the center of the roll.

An acid resist coating is placed on the entire surface of the second roll and the roll is rotated in contact with the machine engraved roll to remove the acid resist coating in a pattern complementing the engraved pattern on the other roll. The roll withthe acid resist coating thereon is placed in an acid bath and etched in accordance with standard procedures. These steps of coating and etching may be repeated a number of times to produce the desired depth of engraving on the acid etched roll. Once the desired depth is obtained, the resultant rolls are a pair of accurately mated steel embossing rolls having a Rockwell C hardness of about 50-60 throughout their entire depth.

It should be realized that the foregoing specific embodiment has been shown and described only for the purpose of illustrating principles of the present invention and is subject to change without departure from such principles. The invention includes all modifications encompassed within the spirit and scope of the appended claims.

I claim:

1. A method of manufacturing a pair of mated steel embossing rolls, said rolls being fully furnace hardened comprising:

a furnace hardening a pair of metal rolls, one of said rolls having a slightly larger diameter than its desired final diameter in the pair of mated rolls,

b normalizing the outer surface of the roll having the slightly larger diameter,

c turning and grinding said normalized surface to the desired final diameter,

d machine engraving said ground normalized surface,

e flame hardening said engraved, normalized surface,

and

f mating the engraved pattern on said flame hardened surface to the other of said rolls.

2. A method according to claim 1 wherein the pair of rolls are furnace hardened to a Rockwell C hardness of from 50 to 60.

3. A method according to claim 1 wherein the outer surface of the roll having the slightly larger diameter is normalized to a depth of from about 7% inch to A inch.

4. A method according to claim 1 wherein the pair of rolls is furnace hardened to a Rockwell C hardness of from 50 to 60 and the machine engraved normalized surface is flame hardened to the same Rockwell C hardness.

5. A method according to claim 1 wherein the machine engraved pattern on the roll is mated to the second roll by acid etching.

6. A method according to claim 1 wherein the pair of rolls are furnace'hardened to a Rockwell C hardness of from 50 to 60, the outer surface of the roll having the slightly larger diameter is normalized to a depth of from bout 1% to A inch, the machine engraved normalized surface is flame hardened to the same Rockwell C hardness as the remainder of the roll and the engraved pattern on the flame hardenedsurface is mated to the other roll by acid etching. 

1. A method of manufacturing a pair of mated steel embossing rolls, said rolls being fully furnace hardened comprising: a furnace hardening a pair of metal rolls, one of said rolls having a slightly larger diameter than its desired final diameter in the pair of mated rolls, b normalizing the outer surface of the roll having the slightly larger diameter, c turning and grinding said normalized surface to the desired final diameter, d machine engraving said ground normalized surface, e flame hardening said engraved, normalized surface, and f mating the engraved pattern on said flame hardened surface to the other of said rolls.
 2. A method according to claim 1 wherein the pair of rolls are furnace hardened to a Rockwell C hardness of from 50 to
 60. 3. A method according to claim 1 wherein the outer surface of the roll having the slightly larger diameter is normalized to a depth of from about 1/8 inch to 1/4 inch.
 4. A method according to claim 1 wherein the pair of rolls is furnace hardened to a Rockwell C hardness of from 50 to 60 and the machine engraved normalized surface is flame hardened to the same Rockwell C hardness.
 5. A method according to claim 1 wherein the machine engraved pattern on the roll is mated to the second roll by acid etching.
 6. A method according to claim 1 wherein the pair of rolls are furnace hardened to a Rockwell C hardness of from 50 to 60, the outer surface of the roll having the slightly larger diameter is normalizEd to a depth of from bout 1/8 to 1/4 inch, the machine engraved normalized surface is flame hardened to the same Rockwell C hardness as the remainder of the roll and the engraved pattern on the flame hardened surface is mated to the other roll by acid etching. 